cc write.cpp
./a.out
cat file.txt
cc read.cpp
./a.out
cc size.cpp
./a.out
du -b file.txt #按字节显示文件大小
cc write1.cpp
./a.out
cat file.txt
cc read.cpp
./a.out
cc read1.cpp
./a.out
cc right.cpp
./a.out
